<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>QQ</title>

    <style type="text/css">
        body {
            margin: 0;
            padding: 0;
        }

        h3 {
            text-align: center;
        }

        .wrapper {
            height: 800px;
            line-height: 800px;
            text-align: center;
            font-size: 200px;
            border: 1px dotted blue;
        }

        .odd {
            background-color: #dedede;
        }

        .even {
            background-color: #ffff00;
        }

        .second {

            background-image: url(fisrtbg.jpg);
            background-repeat: no-repeat;
            background-position: center;
            background-size: cover;
            background-attachment: fixed;

            /* background: #ffff00 url(fisrtbg.jpg) center no-repeat  fixed ;
                background-size: contain ; */
        }

        .fourth {

            background-image: url(secondbg.jpg);
            background-repeat: no-repeat;
            background-position: center;
            background-size: cover;
            background-attachment: fixed;

            /* background: #ffff00 url(secondbg.jpg) left top/80% 50% no-repeat fixed; */
        }

        .sixth {
            background-image: url(thirdbg.jpg);
            background-repeat: no-repeat;
            background-position: center;
            background-size: cover;
            background-attachment: fixed;
        }
    </style>
</head>

<body>

    <div class="wrapper odd first"></div>

    <div class="wrapper even second"></div>

    <div class="wrapper odd third"></div>

    <div class="wrapper even fourth"></div>

    <div class="wrapper odd fifth"></div>

    <div class="wrapper even sixth"></div>

    <div class="wrapper odd seventh"></div>

</body>

</html>